Item Mo-706 Prefabricated Underdrains

ITEM MO-706 PREFABRICATED UNDERDRAINS

DESCRIPTION

706-1.1 This item shall consist of the installation of prefabricated underdrains in accordance with these specifications and in reasonably close conformity with the lines and grades shown on the plans or as directed by the Engineer.

MATERIALS

706-2.1 GENERAL. The prefabricated underdrains and laterals shall be of the type called for on the plans or in the proposal and shall be in accordance with the following appropriate requirements.

706-2.2 PREFABRICATED UNDERDRAIN. The prefabricated underdrain shall consist of a non- woven needle punched polyethylene geotextile meeting the following requirements:

Tensile Strength 90 lb. min. (ASTM D-4632) Elongation 50% (ASTM D-4632) Burst Strength 150 psi min. (ASTM D-3786) Puncture Strength 45 psi min. (ASTM D-3787 mod) Permeability K=0.20 cm / sec. min. (ASTM D-4491) Trapezoidal Tear 40 lbs (ASTM D-4533) Apparent Opening Size 70 (ASTM D-4751) (Equivalent U.S. Sieve)

The geotextile shall tightly encapsulate an internal polyethylene core meeting the following requirements:

Composition Polyethylene (ASTM D-1248) Water Absorption 0.05% at 24 hours (ASTM D-570) Fungus Resistance No growth (ASTM G-21)

The product shall allow the entry of water from all sides of the core and shall be designed to minimize fabric intrusion into the core. When a one sided core is used, the core shall have at least 5 percent of its area in unobstructed inflow through the back or shoulder side and at least 65 percent on the front or pavement side.

The geocomposite underdrain shall have a minimum compressive strength of 55 psi with a maximum deformation of 20% when tested in accordance with ASTM D-1621 and an in plane flow of 15 gpm / ft of width in a soil environment in accordance with ASTM D-4716*.

*ASTM D-4716 at a 10 psi load after 100 hours at a hydraulic gradient of 0.1. If a core separates the flow channel into two or more parts, only the flow rate of the channel facing the pavement side will be considered.

Fittings for outlet pipe connections shall conform to the manufacturer's recommendations. The fittings must be capable of maintaining the integrity of the system under long-term loads and provide efficient and unrestricted flow.

Couplings used to join rolls of material shall conform to the manufacturer's recommendations. They must provide a positive connection that will prevent pull-apart during installation procedures. All connections between the drain and fittings/couplings should be soil tight as recommended by the manufacturer.

1 Rev. 04/01/02 Prior to the use of materials, the contractor shall furnish manufacturer’s certified test reports to the Engineer for those materials proposed for use during construction. The certified test reports shall include a statement that the materials meet the specification requirements. The certification and test results shall be submitted to the Engineer at least 30 days prior to installation.

At the option of the Engineer, materials delivered to the job site may be sampled and tested by an independent testing lab to assure compliance to these specifications. Failure to meet these test requirements shall result in rejection of the lot of material and removal from the job site.

706-2.3 OUTLET PIPE MATERIALS. The outlet pipe shall be a 4-inch diameter corrugated polyethylene (PE) drainage tubing conforming to AASHTO M 252.

706-2.4 CONCRETE. The concrete for splash pads shall be proportioned, placed, and cured in accordance with Item MO-610, Structural Portland Cement Concrete.

706-2.5 REINFORCING STEEL. Reinforcing bars for splash pad outlet construction shall be deformed steel bars conforming to the requirements of the “Specification for Deformed Billet-Steel Bars for Concrete Reinforcement”, ASTM Designation: A615, Grade 60.

706-2.6 AGGREGATE BACKFILL. Aggregate backfill shall be a crushed limestone or dolomite and shall conform to either gradation in the table when tested in accordance with ASTM C 136.

Sieve Designations Percentage by Weight Passing Sieves (Square Openings) Gradation A Gradation B (MoDOT Gradation D) (MoDOT Gradation E) 1 inch 100 --- 3/4 inch 90-100 100 1/2 inch --- 80-100 3/8 inch 15-45 40-70 No. 4 0-8 0-10 No. 8 --- 0-4

CONSTRUCTION

706-3.1 EQUIPMENT. All equipment necessary and required for the proper construction of the underdrain system shall be on the project, in first-class working condition, and approved by the Engineer before construction is permitted to start.

The Contractor shall provide hand tampers and pneumatic tampers to obtain the required compaction of the pipe bed and backfill, as specified.

706-3.2 EXCAVATION. The Contractor shall do all necessary excavation to the grades shown on the plans. The width of the trench shall be not less than eight inches (8”). The excavation shall be unclassified and shall be performed regardless of the material encountered.

The excavation shall not be carried below the required depth, when this is done, the trench shall be backfilled at the Contractor’s expense with material approved by the Engineer and compacted to the density requirements under Item MO-152.

2 Rev. 04/01/02 The grades shown on the plans are to the flow line of the underdrain.

706-3.3 INSTALLING PREFABRICATED UNDERDRAINS. Before any underdrain material is placed, the underlying course shall be checked and accepted by the Engineer. The underdrain shall be installed in accordance with the manufacturer’s recommendations and as specified herein.

During the placing of the underdrain, caution shall be used to avoid damage to the fabric. Any damage to the fabric shall be repaired or replaced by the Contractor to the satisfaction of the Engineer. No additional payment will be made for repairing or replacing the damaged area.

706-3.4 INSTALLING OUTLET PIPES. The prefabricated underdrain manufacturer shall provide fittings and materials necessary to make splices in the product and to provide outlet connections compatible with the outlet piping (laterals) specified on the plans. The fittings, materials and outlet connections shall be designed and installed to prevent soil intrusion into the core of the underdrain and the underground storm sewer pipe. Place the outlet pipes to the elevations indicated on the plans.

706-3.5 SPLASH PADS. When shown on the plans, splash pads shall be constructed at the underdrain outlet locations. The area shall be excavated and compacted, as described in the corresponding splash pad detail, prior to the placement of the forms.

706-3.6 CONNECTIONS. When the plans call for connections to existing or proposed pipe or structures, these connections shall be watertight and made so that a smooth uniform flow line will be obtained throughout the drainage system. Openings in existing pipes or inlets shall be made by drilling or other approved methods. The opening shall not be larger than the pipe diameter plus 1 inch.

706-3.7 HANDLING AND STORAGE. The prefabricated underdrain product shall be shipped, stored and handled so as to prevent excessive exposure to sunlight, which would result in fabric deterioration. At the minimum, the underdrain shall be shipped encapsulated in the protective wrapping.

706-3.8 BACKFILLING.

A. Prefabricated Underdrain. Before any aggregate backfill material is placed, the prefabricated underdrain installation shall be checked and approved by the Engineer. Aggregate backfill material shall be placed as shown on the Plans. The aggregate backfill shall be placed in layers not exceeding 8 inches in depth and lightly compacted by hand or pneumatic tampers as directed by the Engineer. Contractor shall exercise care not to damage the prefabricated underdrain during the placement and compaction of the aggregate backfill. Any prefabricated underdrain damaged during the placement and compaction of the aggregate backfill shall be replaced at the Contractor’s expense. The top of the trench shall be backfilled with Engineer approved earth as indicated.

B. Outlet Pipes. The outlet pipe trench shall be backfilled immediately after the pipe is installed. The backfill material shall be selected material from excavation or borrow. Material shall not contain stones retained on a 1-inch sieve, frozen lumps, lumps retained on a 2-inch sieve, or any other material, which is objectionable to the Engineer. The material shall be moistened or dried, if necessary to be compacted as specified. Backfill material shall be approved by the Engineer. The backfill shall be placed in loose layers not exceeding 6 inches in depth. Successive layers shall be added and thoroughly compacted by hand and pneumatic tampers, approved by the Engineer, until the trench is completely filled and brought to the proper elevation. Backfilling shall be done in a manner to avoid injurious top or side pressures on the pipe. The backfill shall be compacted to the density required under Item MO-152.

3 Rev. 04/01/02 706-3.9 CLEANING AND RESTORATION OF SITE. After the backfill is completed, the Contractor shall dispose of all excess material, dirt and rubbish from the site. Excess earth may be deposited in embankments, shoulders, or as ordered by the Engineer. The Contractor shall restore all disturbed areas to their original condition.

After all work is completed, the Contractor shall remove all tools and equipment, leaving the entire site free, clear and in good condition.

Performance of the work described in this section is not payable directly but shall be considered as a subsidiary obligation of the Contractor, covered under the contract unit price for the underdrain.

METHOD OF MEASUREMENT

706-4.1 Measurement of prefabricated underdrain shall be made by the number of linear feet of underdrain in place completed and accepted, to be measured along the centerline of the drain, and shall include trenching, aggregate backfill, earth backfill, wasting of excess excavated material and all other materials and labor required to complete this item.

706-4.2 Measurement of PE outlet pipe will be by the number of linear feet of pipe in place, completed and accepted, to be measured along the centerline of the pipe from end to end. All fittings will be included in the footage as typical pipe sections.

706-4.3 Measurement of splash pads shall be made by the number of splash pads installed, completed and accepted.

706.4.4 Measurement of connections to existing pipes or structures will be made by the number of connections made to existing systems that are completed and approved. All materials as well as excavating, backfilling, grouting, drilling, jackhammering, etc. and all labor required to make a watertight connection that provides a smooth uniform flow line into the existing pipe or structure will be included in the unit price for each connection.

BASIS OF PAYMENT

706-5.1 Payment will be made at the contract unit price per linear foot for prefabricated underdrain; at the contract unit price per linear foot for 4” PE Outlet Pipe; at the contract unit price per each for splash pads; and at the contract unit price per each for connections to existing pipes or structures. These prices shall be full compensation for furnishing all materials and for all preparation, hauling, and installation of these materials, all excavation and earth backfill, and for all labor, equipment, tools, and incidentals necessary to complete the item.

Payment will be made under:

Item MO-706-5.1 [ ] Prefabricated Underdrain -- per linear foot

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * The Engineer shall specify the size of the prefabricated underdrain shown in the plans. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Item MO-706-5.2 4” PE Outlet Pipe -- per linear foot

Item MO-706-5.3 Splash Pad -- per each

4 Rev. 04/01/02 Item MO-706-5.4 Connection to existing pipe or structures -- per each

MATERIAL REQUIREMENTS

ASTM C-136 Sieve or Screen Analysis of Fine and Course Aggregates

ASTM D-570 Water Absorption of Plastics

ASTM D-1248 Polyethylene Plastics Molding and Extrusion Materials

ASTM D-1621 Compressive Properties of Rigid Cellular Plastics

ASTM D-1876 Peel Resistance of Adhesives

ASTM D-3786 Hydraulic Bursting Strength of Knitted Goods and Non-Woven Fabrics

ASTM D-3787 Mod. Bursting Strength of Knitted Goods

ASTM D-4491 Water Permeability of Geotextiles

ASTM D-4533 Deterioration of Geotextiles from Exposure to Ultraviolet Light and Water

ASTM D-4632 Breaking Load and Elongation of Geotextiles

ASTM D-4716 Constant Head Hydraulic Transmissivity (In-Plane Flow) of Geotextiles

ASTM D4751 Standard Test Method for Determining Apparent Opening Size of a Geotextile

ASTM G-21 Resistance of Synthetic Polymeric Materials to Fungi

ASSHTO M 252 Corrugated Polyethylene Drainage Tubing

5 Rev. 04/01/02